With widespread use of a wide-area Ethernet service, an encryption apparatus in layer 3 (the network layer of the Open Systems Interconnection (OSI) reference model) and an encryption apparatus in layer 2 (the link layer of the OSI reference model) have become used. However, it may be difficult to apply Cipher Block Chaining (CBC) encryption to the apparatus in layer 2. Moreover, when CBC is applied to a communication apparatus, a communication frame size may be increased which causes a decrease in communication speed.
Accordingly, there is a need for a method and system that enhances confidentiality of information in cryptographic communication without increasing the communication frame size or processing time.